Currently, in networks adapted to operate under adaptive multi-rate (AMR) speech coding having at least one codec having a robust coding, the spectrum efficiency and capacity requirements are high. In particular, the above requirements are highlighted when there are many terminals using the network. For speech, the introduction of the robust coding makes it possible to tighten the network reuse. Furthermore, the robust codec allows the network to operate at very low Carrier-to-Interference Ration (CIR) values. The communication comprises the Traffic Channel (TCH) and the associated control channel (ACCH). Nevertheless, the ACCH are kept the same although robust coding in TCH is applied. In a high capacity robust coding based network, the CIR values can be occasionally low (e.g. few dBs). However, at this level the associated control channel error rates are really disturbing resulting in rectification actions in the network.
Such a known technique is disclosed the current GSM/EDGE Radio Access Networks (GERAN networks). I.e. in GERAN networks the spectrum efficiency and capacity requirements are very high. For speech, the introduction of AMR (Adaptive Multi-rate) makes it possible to tighten the network reuse to unprecedented level. AMR has very robust codecs (e.g. AMR4.75, AMR5.9) that allow the network to operate at very low CIR values. However, when AMR was standardized, the associated control channels were kept the same. Examples of the associated control channels are Slow Associated Control Channel (SACCH) and Fast Associated Control Channel (FACCH)) in GERAN. In a high-capacity AMR network, the CIR values can be occasionally very low (only few dBs). For example, AMR4.75 can reach 1% Frame Error Rate with only CIR of 2.6 dB. However, at this level the SACCH and FACCH error rates are around 50%.
Failed SACCH decoding(s) will cause the call to be dropped, based on RADIO_LINK_TIMEOUT parameter. Failed SACCH and FACCH decoding(s) cause also problems with L3-layer signaling, measurement reports and RRM algorithms (handover, power control).
Hence, the bottleneck and a clear drawback for network capacity will often be the associated control channels.